/Engine/Plugins/Animation/IKRig/Source/IKRigEditor/Public/RigEditor/IKRigController.h
Returns true if this is a valid chain. Produces array of bone indices between start and end (inclusive). Optionally provide a runtime skeleton from an IKRigProcessor to get indices for a running instance (otherwise uses stored hierarchy in asset)
bool ValidateChain ( const [FName](API\Runtime\Core\UObject\FName) ChainName, const [FIKRigSkeleton](API\Plugins\IKRig\Rig\FIKRigSkeleton) * OptionalSkeleton, [TSet](API\Runtime\Core\Containers\TSet)< int32 > & OutChainIndices ) const